n-alkylmonoamine into crystalline lamellar titanium phenylphosphonate

Crystalline lamellar titanium phenylphosphonate was intercalated with n-alkylmonoamines, H₃C(CH₂)_n-NH₂ (n=0 to 3), which decomposed on heating in four distinct stages. The lamellar compound was calorimetrically titrated with ethanolic amine solution at 298.15±0.02 K and the enthalpy, Gibbs free energy and entropy were calculated. with the exception of butylamine, the enthalpic values increased with the number of carbon atoms in the amine chain, as -16.20±0.22; -18.70±0.19; -23.70±0.24 and -18.30±0.22 kj mol^-1, from n=0 to 3. The exothermic enthalpic values reflected a favorable energetic process of intercalation, when the solvated ethanol molecules on inorganic matrix are progressively substituted by solute. The negative gibbs free energy results supported the spontaneity of the reactions and the positive favorable entropic values are in agreement with the increase of solvent molecules in the reaction medium, as the amine becomes bonded to the crystalline lamellar inorganic matrix. This revised version was published online in July 2006 with corrections to the Cover Date.     

Layered Crystalline Barium Phenylphosphonate as Host Support for <Emphasis Type="Italic">n</Emphasis>-Alkylmonoamine Intercalation

Layered barium phosphonate, synthesized by combining the metallic salt with a phenylphosphonic acid solution, yielded Ba(HO₃PC₆H₅)₂ ·H₂O (BaPP), which gives the corresponding anhydrous compound on heating. n-Alkylmonoamines intercalation into the crystalline lamellar precursor resulted in compounds having the general formula Ba(HO₃PC₆H₅)₂ ·xH₂N(CH₂) _n CH₃ ·(1−x)H₂O (n=1–5). The intense infrared bands in the 1160–695 cm⁻¹ interval confirmed the presence of the phosphonate groups attached to the inorganic layer, with sharp and intense peaks in X-ray diffraction patterns for both hydrated and anhydrous compounds. The thermogravimetric curves for both supports showed the release of water molecules and the organic moiety in distinct stages to yield a final Ba(PO₃)₂residue. An additional amine mass loss steps was observed for the corresponding aminated compounds. One isolated DSC peak found in the layered precursor compound contrasts by its absence in the anhydrous form and the ³P NMR spectrum presented one peak for attached phenylphosphonate groups centered at 12.4 ppm. An increase in carbon and hydrogen percentages for intercalated compounds followed the amine size chain with a corresponding decrease in nitrogen percentage. The interlayer distance (d) correlates linearly with the number of carbon atoms (n _c ) of the alkylamine chains, d=1467 + 62n _c and d=1688 + 60n _c , for the hydrated and anhydrous compounds, respectively, permitting inference of the interlayer distance for an unknown amine.This revised version was published online in July 2005 with a corrected issue number.     

Kinetics of the R + HBr RH + Br (CH3CHBr, CHBr2 or CDBr2) equilibrium. Thermochemistry of the CH3CHBr and CHBr2 radicals

The kinetics of the reaction of the CH₃CHBr, CHBr₂ or CDBr₂ radicals, R, with HBr have been investigated in a temperature-controlled tubular reactor coupled to a photoionization mass spectrometer. The CH₃CHBr (or CHBr₂ or CDBr₂) radical was produced homogeneously in the reactor by a pulsed 248 nm exciplex laser photolysis of CH₃CHBr₂ (or CHBr₃ or CDBr₃). The decay of R was monitored as a function of HBr concentration under pseudo-first-order conditions to determine the rate constants as a function of temperature. The reactions were studied separately from 253 to 344 K (CH₃CHBr + HBr) and from 288 to 477 K (CHBr₂ + HBr) and in these temperature ranges the rate constants determined were fitted to an Arrhenius expression (error limits stated are 1σ + Student’s t values, units in cm³ molecule⁻¹ s⁻¹, no error limits for the third reaction): k(CH₃CHBr + HBr) = (1.7 ± 1.2) × 10⁻¹³ exp[+ (5.1 ± 1.9) kJ mol⁻¹/RT], k(CHBr₂ + HBr) = (2.5 ± 1.2) × 10⁻¹³ exp[−(4.04 ± 1.14) kJ mol⁻¹/RT] and k(CDBr₂ + HBr) = 1.6 × 10⁻¹³ exp(−2.1 kJ mol⁻¹/RT). The energy barriers of the reverse reactions were taken from the literature. The enthalpy of formation values of the CH₃CHBr and CHBr₂ radicals and an experimental entropy value at 298 K for the CH₃CHBr radical were obtained using a second-law method. The result for the entropy value for the CH₃CHBr radical is 305 ± 9 J K⁻¹ mol⁻¹. The results for the enthalpy of formation values at 298 K are (in kJ mol⁻¹): 133.4 ± 3.4 (CH₃CHBr) and 199.1 ± 2.7 (CHBr₂), and for α-C–H bond dissociation energies of analogous compounds are (in kJ mol⁻¹): 415.0 ± 2.7 (CH₃CH₂Br) and 412.6 ± 2.7 (CH₂Br₂), respectively.     

The O–H···O, O–H···N and C–H···O hydrogen bonds in 1,4-dimethylpiperazine mono-betaine monohydrate

1,4-Dimethylpiperazine mono-betaine (1-carboxymethyl-1,4-dimethylpiperazinium inner salt, MBPZ) crystallizes as monohydrate. The crystals are orthorhombic, space group Pccn. Two MBPZ molecules and two water molecules form a cyclic oligomer, (MBPZ·H₂O)₂. The O–H···O and O–H···N hydrogen bonds are of 2.769(1) and 2.902(1) Å, respectively. The dimers interact with the neighboring molecules through the C–H···O hydrogen bonds of 3.234(1) Å. The piperazine ring assumes a chair conformation with the N(4)–CH₃ and N⁺(1)–CH₂COO⁻ groups in the equatorial position and the N⁺(1)–CH₃ group in the axial one. The FTIR spectrum is compared with that calculated by the B3LYP/6-31G(d,p) level of theory.     

Self-assembly of the pre-formed inclusion complexes between cyclodextrins and alkanethiols on gold electrodes

A new kind of self-assembled monolayer (SAM) formed in aqueous solution through the pre-formed inclusion complexes (abbreviated CD · C_n) between α, β-cyclodextrins (CDs) and alkanethiols (CH₃(CH₂)_n−1)SH, n = 10, 14 and 18) was prepared successfully on gold electrodes. High-resolution ¹H NMR was used to confirm the formation of CD · C_n. X-ray photoelectron spectroscopy, cyclic voltammetry and chronoamperometry were used to characterize the resulting SAMs (denoted as M_CD·Cn). It was found that M_CD·Cn were more stable against repeated potential cycling in 0.5 M H₂SO₄ than SAMs of CH₃(CH₂)_n−1SH (denoted as M_Cn), with a relative sequence of M_β−CD·Cn > M_α−CD·Cn > M_Cn. In addition, an order of blocking the electron transfer between gold electrodes and redox couples (both Fe(CN)³₆ and Ru(NH₃)³⁴₆) in solution, M_CD·C10 > M_CD·C14 > M_CD·C18, was observed. A plausible explanation is provided to elucidate some of the observations.     

UV–visible spectrum of the phenyl radical and kinetics of its reaction with NO in the gas phase

Pulse radiolysis transient UV–visible absorption spectroscopy was used to study the UV–visible absorption spectrum (225–575 nm) of the phenyl radical, C₆H₅(), and kinetics of its reaction with NO. Phenyl radicals have a strong broad featureless absorption in the region of 225–340 nm. In the presence of NO phenyl radicals are converted into nitrosobenzene. The phenyl radical spectrum was measured relative to that of nitrosobenzene. Based upon σ(C₆H₅NO)_{270 nm}=3.82×10⁻¹⁷ cm² molecule⁻¹ we derive an absorption cross-section for phenyl radicals at 250 nm, σ(C₆H₅())_{250 nm}=(2.75±0.58)×10⁻¹⁷ cm² molecule⁻¹. At 295 K in 200–1000 mbar of Ar diluent k(C₆H₅()+NO)=(2.09±0.15)×10⁻¹¹ cm³ molecule⁻¹ s⁻¹.     

Silylating Agents Grafted onto Silica Derived from Leached Chrysotile

Silica from leached chrysotile fibers (SILO) was silanized with trialkoxyaminosilanes to yield inorganic–organic hybrids designated SILx (x=1–3). The greatest amounts of the immobilized agents were quantified as 2.14, 1.90, and 2.18 mmol g⁻¹ on SIL1, SIL2, and SIL3 for –(CH₂)₃NH₂,–(CH₂)₃NH(CH₂)₂NH₂, and –(CH₂)₃NH(CH₂)₂NH(CH₂)₂NH₂ groups attached to the inorganic support. The infrared spectra for all modified silicas showed the absence of the Si–OH deformation mode, originally found at 950 cm⁻¹, and the appearance of asymmetric and symmetric C–H stretching bands at 2950 and 2840 cm⁻¹. Other important bands associated with the organic moieties were assigned to ν_as(NH) at 3478 and ν_sym(NH) at 3418 cm⁻¹. The NMR spectrum of the solid precursor material suggested two different kinds of silicon atoms: silanol and siloxane groups, between −90 and 110 ppm; however, additional species of silicon that contain the organic moieties bonded to silicon at −58 and −66 ppm appeared after chemical modification. These modified silicas showed a high adsorption capacity for cobalt and copper cations in aqueous solution, in contrast to the original SILO matrix, confirming the unequivocal anchoring of silylating agents on the silica surface.     

Cluster-assisted decomposition reactions of the molecular anions of SF6 and C7F14

The cluster ions formed by the attachment of dimethylsulfoxide (DMSO) and methanol to the molecular negative ions of C₇F₁₄ and SF₆ have been studied by a pulsed e-beam high pressure mass spectrometer (PHPMS) and by an atmospheric pressure ionization mass spectrometer (APIMS). The free energy change (ΔG°) for the clustering equilibria reaction, M⁻ + S M⁻S, at 35 °C are found to be −7.7 and −7.s kcal/mol for S = DMSO and M⁻ = C₇F⁻₁₄ and SF⁻₆, respectively, and −6.4 and −4.5 kcal/mol for S = methanol and M⁻ = C₇F⁻₁₄ and SF⁻₆, respectively. While the cluster ions formed by DMSO are found to be stable against side reactions, those formed by methanol undergo decomposition processes in which the central core ion is fragmented. At 35 °C, the rate law for the decomposition of the SF⁻₆ (CH₃OH)₁ ion is second-order, involving the M⁻ (CH₃OH)₁ cluster ion and another methanol molecule. While the C₇F⁻₁₄(CH₃OH)₁ ion also decomposes through this second-order process, a competing unimolecular mechanism is also operative at 35 °C. With increases in the PHPMS ion source temperature to 150 °C, the unimolecular decomposition process becomes progressively dominant for both of the M⁻(CH₃OH)₁ cluster ions of C₇F₁₄ and SF₆. Methanol cluster ions of the type M⁻S₂ are not observed under any of the conditions examined here. When methanol or water partial pressures of a few torr or higher are present in the buffer gas of the APIMS ion source, the decomposition reactions are very fast and only the fragment ions produced by these reactions are observed in the electron-capture (EC)-APIMS spectra of C₇F₁₄ and SF₆. Also, in the methanol-containing APIMS ion source, the course of the SF⁻₆ decomposition reaction is altered so that fragment ions of the type F⁻(S)_n dominate the EC-APIMS spectrum of SF₆ at all ion source temperatures. For C₇F₁₄, fragment ions of the type F⁻(S)_n become dominant at lower ion source temperatures. These previously unknown reactions are expected to be important in the analysis of perfluorinated compounds by mass spectrometric methods that utilize ionization by electron capture or negative chemical ionization. The nature of the fragment ions produced in these cluster-assisted reactions may also provide a new source of information concerning the structures of the molecular negative ions of SF₆ and C₇F₁₄.     

Voltammetric studies on the α-tocopherol anion and α-tocopheroxyl (Vitamin E) radical in acetonitrile

The α-tocopheroxyl radical was generated voltammetrically by one-electron oxidation of the α-tocopherol anion (E ^r_1/2=−0.73 V versus Ag|Ag⁺) that was prepared by reacting α-tocopherol with Et₄NOH in acetonitrile (with Bu₄NPF₆ as the supporting electrolyte). Cyclic voltammograms recorded at variable scan rates (0.05–10 V s⁻¹), temperatures (−20 to 20°C) and concentrations (0.5–10 mM) were modelled using digital simulation techniques to determine the rate of bimolecular self-reaction of α-tocopheroxyl radicals. The k values were calculated to be 3×10³ l mol⁻¹ s⁻¹ at 20°C, 2×10³ l mol⁻¹ s⁻¹ at 0°C and 1.2×10³ l mol⁻¹ s⁻¹ at −20°C. In situ electrochemical-EPR experiments performed at a channel electrode confirmed the existence of the α-tocopheroxyl radical.     

Determination of C4–C14 carboxylic acids by capillary zone electrophoresis: Application to the identification of diamide degradation products and partitioning studies

Capillary zone electrophoresis (CZE) was investigated for the determination of linear saturated carboxylic acid homologues ranging from C₄ to C₁₄. Separation conditions were optimised to overcome the problems of decreasing solubility and decreasing selectivity between successive homologues with increasing chain length. Separations were performed at 20°C, using a 20 kV separation voltage and a pH 8 electrolyte containing 30% methanol. A suitable chromophore (4-aminobenzoate) was added to ensure indirect UV detection of the analytes. Calibration curves and repeatability were established. Minimum detectable concentrations of 3·10⁻⁶ mol l⁻¹ were achieved. Resolution between successive homologues was better than 2. The electrophoretic mobility of each homologue (n=7–14) was assessed and a quasi-linear relationship between the mobility value and 1/n was observed. The quantitative analysis of a diamide degradation solution was performed and compared to potentiometric results. The CZE method was also applied to the determination of C₇–C₁₄ partitioning between an organic medium containing tributylphosphate in n-dodecane and different basic solutions. Their behaviour was established according to the chain length and the pH of the aqueous phase. For C₁₀–C₁₄ compounds, results were validated by comparison with gas chromatographic analysis of the organic phases.     

Structures, vibrational frequencies, and electron affinities of SF5On/SF5On (n = 1–3)

The molecular structures, vibrational frequencies, and electron affinities of the SF₅O_n/SF₅O_n⁻ (n = 1–3) species have been examined with four hybrid density functional theory (DFT) methods. The basis set used in this work is of double-ζ plus polarization quality with additional diffuse s- and p-type functions, denoted DZP++. The geometries are fully optimized with each DFT method independently. The SF₅O_n (n = 1–3) species should be potential greenhouse gases. The anion SF₅O₂⁻ with C_s symmetry has a ³A″ electronic state, and the neutral SF₅O₃ with ²A″ electronic state has C_s symmetry. The anions SF₅O₂⁻ and SF₅O₃⁻ should be regarded as SF₅⁻·O₂ and SF₅O⁻·O₂ complexes, respectively. Three different types of the neutral–anion energy separation presented in this work are the adiabatic electron affinity (EA_ad), the vertical electron affinity (EA_vert), and the vertical detachment energy (VDE). The EA_ad values predicted by the B3PW91 method are 5.22 (SF₅O), 4.38 (SF₅O₂), and 3.61 eV (SF₅O₃). Compared with the experimental vibrational frequencies, the BHLYP method overestimates the frequencies, and the other three methods underestimate the frequencies. The bond dissociation energies D_e (SF₅O_n → SF₅O_n−m + O_m) for the neutrals SF₅O_n and D_e (SF₅O_n⁻ → SF₅O_n−m⁻ + O_m and SF₅O_n⁻ → SF₅O_n−m + O_m⁻) for the anions SF₅O_n⁻ are reported.     

Vermiculite-aliphatic amine interactions at the solid/liquid interface: a thermodynamic approach

Polar n-alkylmonoamines of general formula H₃C(CH₂) _n NH₂ (n = 1, 3, 5) interacted with layered silicate vermiculite at the solid/liquid interface. The maximum amount of amine intercalated (N _f ) inside the interlamellar space were 0.62, 0.46, and 0.38 mmol g⁻¹, to give the following order of intercalation ethyl → butyl → hexylamines. The layered vermiculite solid was suspended in deionized water and calorimetrically titrated with this series of amines, to give favorable thermodynamic data, such as exothermic enthalpy, negative Gibbs free energy and positive entropy data.     

Spectroscopic and antimicrobial studies of La, Pr, Nd and Gd complexes of a dipodal [N,N,N] chelating ligand

The lanthanide complexes of bis(benzimidazole-2′-yl-methyl)amine (BImz) having molecular formula [M(BImz)X₃H₂O]·nH₂O (M = La, Pr, Nd, or Gd; X = Cl or ClO₄ and n = 1, 2 or 3) were prepared and characterized spectroscopically through IR, ¹H and ¹³C NMR, FAB-mass, UV–visible and luminescence spectroscopy. TGA data suggested presence of coordinated and the lattice water. The oscillator strengths of the f–f transitions and the covalency parameters (β, b^1/2 and δ) have been evaluated from the electronic spectral data. The proposed hepta-coordinate geometry for the complexes has been ascertained from the molecular model computations. CV studies indicate formation of a stable quasi-reversible redox couple Gd^III/IV in the solution. The in vivo antimicrobial activities of the complexes have been evaluated against gram +ve and gram −ve bacteria and fungi.     

Dinitrogen and carbon monoxide hydrogen bonding in protonic zeolites: Studies from variable-temperature infrared spectroscopy

Adsorption (at a low temperature) of nitrogen on the protonic zeolite H-Y results in hydrogen bonding of the adsorbed N₂ molecules with the zeolite Si(OH)Al Brønsted-acid groups. This hydrogen-bonding interaction leads to activation, in the infrared, of the fundamental N–N stretching mode, which appears at 2334 cm⁻¹. From infrared spectra taken over a temperature range, the standard enthalpy of formation of the OH···N₂ complex was found to be ΔH⁰ = −15.7(±1) kJ mol⁻¹. Similarly, variable-temperature infrared spectroscopy was used to determine the standard enthalpy change involved in formation of H-bonded CO complexes for CO adsorbed on the zeolites H-ZSM-5 and H-FER; the corresponding values of ΔH⁰ were found to be −29.4(±1) and −28.4(±1) kJ mol⁻¹, respectively. The whole set of results was analysed in the context of other relevant data available in the literature.     

High-accuracy determination of iron in seawater by isotope dilution multiple collector inductively coupled plasma mass spectrometry (ID-MC-ICP-MS) using nitrilotriacetic acid chelating resin for pre-concentration and matrix separation

In the present paper we describe a robust and simple method to measure dissolved iron (DFe) concentrations in seawater down to <0.1 nmol L⁻¹ level, by isotope dilution multiple collector inductively coupled plasma mass spectrometry (ID-MC-ICP-MS) using a ⁵⁴Fe spike and measuring the ⁵⁷Fe/⁵⁴Fe ratio. The method provides for a pre-concentration step (100:1) by micro-columns filled with the resin NTA Superflow of 50 mL seawater samples acidified to pH 1.9. NTA Superflow is demonstrated to quantitatively extract Fe from acidified seawater samples at this pH. Blanks are kept low (grand mean 0.045 ± 0.020 nmol L⁻¹, n = 21, 3× S.D. limit of detection per session 0.020–0.069 nmol L⁻¹ range), as no buffer is required to adjust the sample pH for optimal extraction, and no other reagents are needed than ultrapure nitric acid, 12 mM H₂O₂, and acidified (pH 1.9) ultra-high purity (UHP) water. We measured SAFe (sampling and analysis of Fe) reference seawater samples Surface-1 (0.097 ± 0.043 nmol L⁻¹) and Deep-2 (0.91 ± 0.17 nmol L⁻¹) and obtained results that were in excellent agreement with their DFe consensus values: 0.118 ± 0.028 nmol L⁻¹ (n = 7) for Surface-1 and 0.932 ± 0.059 nmol L⁻¹ (n = 9) for Deep-2. We also present a vertical DFe profile from the western Weddell Sea collected during the Ice Station Polarstern (ISPOL) ice drift experiment (ANT XXII-2, RV Polarstern) in November 2004–January 2005. The profile shows near-surface DFe concentrations of 0.6 nmol L⁻¹ and bottom water enrichment up to 23 nmol L⁻¹ DFe.     

Heat capacity, enthalpy and entropy of strontium niobate Sr2Nb2O7 and calcium niobate Ca2Nb2O7

The heat capacity and the enthalpy increments of strontium niobate Sr₂Nb₂O₇ and calcium niobate Ca₂Nb₂O₇ were measured by the relaxation time method (2–300 K), DSC (260–360 K) and drop calorimetry (720–1370 K). Temperature dependencies of the molar heat capacity in the form C_pm = 248.0 + 0.04350T − 3.948 × 10⁶/T² J K⁻¹ mol⁻¹ for Sr₂Nb₂O₇ and C_pm = 257.2 + 0.03621T − 4.434 × 10⁶/T² J K⁻¹ mol⁻¹ for Ca₂Nb₂O₇ were derived by the least-square method from the experimental data. The molar entropies at 298.15 K, S_m°(298.15 K) = 238.5 ± 1.3 J K⁻¹ mol⁻¹ for Sr₂Nb₂O₇ and S_m°(298.15 K) = 212.4 ± 1.2 J K⁻¹ mol⁻¹ for Ca₂Nb₂O₇, were evaluated from the low-temperature heat capacity measurements.     

3-(4-Tolylazo)phenylboronic acid as the active component of polyhydroxy compounds-selective electrodes

Ionophoric, extraction, acidic and hydrophobic properties of 3-(4-tolylazo)phenylboronic acid (TAPBA) were studied. Determined K_d value equals to 36±2, pK_a equals to 8.6±0.5. TAPBA extracts dobutamine from water into chloroform and transports it across a bulk chloroform membrane. The recovery is 83% (pH=7.5), the transport rate – (6.5±0.5)×10⁻⁷ mol/h. ¹H and ¹³C NMR data confirm the formation of an 1:1 complex between arylboronic acid and catecholamine. TAPBA was used as electrode-active component of plasticized membrane electrodes with cationic and anionic responses to catecholamines and phenolic acids, respectively. For the diethyl sebacate-plasticized membrane, a slope of electrode function to dobutamine is 56±2 mV/decade; the detection limit is 1.3×10⁻⁵ mol/l; the linear range – 5×10⁻⁵–1×10⁻² mol/l; the working pH-range – 4.8–7.6; the response time – 5–10 s. ISE gives incomplete cationic function to less lipophilic catecholamines. The membrane with cationic additive shows an anionic response to caffeic acid in wide pH range.     

The LIF excitation spectra of jet-cooled 3-aminobiphenyl

The S₁←S₀ transitions in 3-aminobiphenyl were studied in a supersonic jet by laser-induced fluorescence. The results were compared with ab initio HF, CIS and DFT/SCI calculations and with experimental data for the biphenyl, 1-phenylpyrrole and 2-phenylindole. The equilibrium geometry of the 3-aminobiphenyl in the S₁ state is non-planar with the dihedral angle between two phenyl rings about 5.4° (CIS/6-31G^*). The torsional potential in the S₁ state has been determined by fitting the one-dimensional potential of the form V(φ)= 2 ∑_n V_n(1−cos nφ), to reproduce the observed level spacing (V₂=3420, V₄=−378, V₆=−32.8 and V₈=−2.9 cm⁻¹). The observed deuteration effects seem to confirm this potential.     

Cyclopalladation of mono-, di- and tribenzylamine by palladium(II) acetate: Influence of bulkiness around the nitrogen atom of benzylamine upon internal metallation

Cyclopalladation of mono-, di- and tribenzylamine has been investigated by reacting the corresponding amines with an equimolar amount of palladium(II) acetate (reaction i), or by heating the corresponding bis-amine complexes [Pd(O₂CMe)₂{(PhCH₂)_nNH_3−n}₂] (n=1, 2) (reaction ii). By the reaction i, all the three amines undergo cyclopalladation. However, in the case of the reaction ii, only the dibenzylamine complex [Pd(O₂CMe)₂{(PhCH₂)₂NH}₂] has been converted into a cyclopalladated complex. The reactivity of the three benzylamines towards cyclopalladation has been discussed in terms of the co-ordinating ability influenced by the bulkiness around the nitrogen atom. Temperature-dependent ¹H-NMR spectra are observed for mononuclear cyclopalladated complexes [Pd(O₂CMe){C₆H₄CH₂N(CH₂Ph)₂–C¹, N}L] (L=PPh₃, AsPh₃) and are attributed to the dissociation of the nitrogen atom in the cyclopalladated chelate ring. A heteroleptic bis-cyclopalladated complex [Pd[C₆H₄CH₂N(CH₂Ph)₂–C¹, N](C₆H₄CH₂NMe₂–C¹, N)] has also been prepared. X-ray crystallographic studies on [{Pd(O₂CMe)[C₆H₄CH₂N(CH₂Ph)₂–C¹, N]}₂] and [Pd[C₆H₄CH₂N(CH₂Ph)₂–C¹, N](C₆H₄CH₂NMe₂–C¹, N)] have been reported.     

Infrared and Raman spectra, conformational stability, normal coordinate analysis, ab initio calculations, and vibrational assignment of 1-fluoro-1-methylsilacyclobutane

The infrared (3500–40 cm⁻¹) spectra of gaseous and solid 1-fluoro-1-methylsilacyclobutane, c-C₃H₆SiF(CH₃), have been recorded. Additionally, the Raman spectrum (3500–30 cm⁻¹) of the liquid has been recorded and quantitative depolarization values have been obtained. Both the axial and equatorial (with respect to the methyl group) conformers have been identified in the fluid phases. Variable temperature (−55–−100°C) studies of the infrared spectra of the sample dissolved in liquid xenon have been carried out. From these data, the enthalpy difference has been determined to be 267±10 cm⁻¹ (3.19±0.12 kJ mol⁻¹), with the axial conformer being the more stable form and the only conformer remaining in the polycrystalline solid. A complete vibrational assignment is proposed for the axial conformer and many of the fundamentals for the equatorial conformer have also been identified. The vibrational assignments are supported by normal coordinate calculations utilizing ab initio force constants. Complete equilibrium geometries have been determined for both rotamers by ab initio calculations employing the 6-31G* and 6-311++G** basis sets at the levels of restricted Hartree–Fock (RHF) and/or Moller–Plesset (MP) to second order. The results are discussed and compared to those obtained for some similar molecules.